1. Technical Field of the Invention
The present invention relates to a semiconductor chip mounting substrate bearing a semiconductor chip thereon. The present invention also relates to an electrooptical device that presents images using an electrooptical material such as a liquid crystal or an electroluminescent material, a liquid-crystal device that presents images by controlling the orientation of the liquid crystal to modulate light, an electroluminescent device that presents images using an organic electroluminescent element, and electronic equipment incorporating the electrooptical device.
2. Description of the Related Art
Electrooptical devices such a liquid-crystal device or an electroluminescent device (hereinafter referred to as an EL device) are widely used as a display unit in electronic equipment such as a mobile computer, a mobile telephone, and a video camera.
The liquid-crystal device with a liquid crystal as an electrooptical material sandwiched between a pair of electrodes controls the orientation of the liquid crystal by controlling a voltage applied to the electrodes, modulating a light beam transmitted through the liquid crystal, and thereby displaying an image such as characters and numerals.
The EL device with an EL light emission layer as an electrooptical material sandwiched between a pair of electrodes controls a voltage applied to these electrodes, thereby controlling a current fed to the EL light emission layer. The light emitted by the light emission layer is thus controlled, displaying an image such as characters and numerals.
In the liquid-crystal device or the EL device, electrodes for sandwiching the liquid crystal or the EL light emission layer are formed on one or a plurality of substrates. For example, the liquid-crystal device includes a pair of substrates facing each other having respective electrodes. On the other hand, the EL device includes, on the surface of one substrate, a pair of electrodes having an EL emission layer sandwiched therebetween. These electrooptical devices have a plurality of electrodes within an effective display area of the substrate, and extension lines extending from the plurality of electrodes, and metal lines, different from the extension lines, are arranged outside the effective display area. The electrodes formed within the effective display area are manufactured of oxides such as ITO, or a metal such as an APC alloy or Cr. When the electrodes are manufactured of a metal, the extension lines extending therefrom are also a metal wire.
For example, the metal lines, different from the extension lines, extending beyond the effective display area, may be used in a circuit board, such as a COG (Chip On Glass) board, on which a semiconductor chip is directly mounted. The metal lines in this case are connected to input terminals of the semiconductor chip, such as input bumps of the semiconductor chip, and connected to an FPC (Flexible Printed Circuit) leading to an external circuit.
It is known that the liquid-crystal device and the EL device employ an electrically conductive oxide such as ITO (Indium Tin Oxide) as a material for electrodes on the substrate, and a metal such as APC or Cr as a material for a metal line formed on the substrate. The APC is an alloy manufactured of Ag (silver), Pd (palladium), and Cu (copper).
The ITO has been widely used as a material for electrodes, etc. The ITO has a high electrical resistivity. If an ITO line is routed for a long path on a substrate, a resulting resistance becomes high, and a driving circuit cannot work normally. Contemplated as a promising material are low electrical resistivity metal such as APC or Cr. For example, resistance of ITO per unit area is 15 ohms, while resistance of Cr per unit area is 1.5 ohms and resistance of APC per unit area is 0.1 ohm. If a wiring pattern is manufactured of such a low resistivity metallic material on a substrate, a wiring pattern having a long length has advantageously a low resistance.
Fabricating a wiring pattern on a substrate of a metal such as APC or Cr advantageously lowers electrical resistance thereof. On the other hand, the use of metals present a new problem. The metal line is subject to corrosion. Due to migration, namely, the transfer of atoms damages the metal line, and the quality of wiring cannot be maintained.
The inventors of the present invention have conducted a variety of experiments in an attempt to resolve the problem of metallic corrosion or migration, and have reached the following conclusion. When a plurality of metal wirings is arranged side by side on a substrate, a potential difference may take place between adjacent wirings. In other words, a relationship of an anode and a cathode is established between the adjacent wirings, and a metallic component of the anode, for example, Ag is considered to dissolve.
In view of the above problem relating to the conventional wiring substrate, the present invention has been developed. It is an object of the present invention to prevent corrosion or migration from taking place in a metal wiring even when a wiring pattern is formed of a low electrical resistivity metallic material.
(1) To achieve the above object, a semiconductor chip mounting substrate of the present invention having a semiconductor chip mounted thereon, includes a power source line for supplying a supply voltage potential to the semiconductor chip, a ground line for supplying a ground voltage potential to the semiconductor chip, an output line to which an output signal from the semiconductor chip is supplied, and an insulator layer for covering the output line, wherein the insulator layer is formed clear of an area between the power source line and the ground line.
The lines formed on the substrate are typically divided into lines routed between an electrode and a driving element and lines routed between an external circuit board and the driving element. Migration mainly takes place in the line routed between the external circuit board and the driving element. The lines routed between the external circuit board and the driving element include power source supply voltage lines such as a power source line and a ground line, a data line for transferring a data signal, and a control signal for controlling drivers, etc.
The inventors have studied the problems, and have found that corrosion and migration take place at almost the same locations, particularly in the power source supply voltage lines. In contrast, the signal lines are almost free from migration. In other words, migration occurs in the power source supply voltage lines which present a large potential difference between adjacent lines.
According the observation of the inventors, the generation of migration is largely dependent on an insulator layer covering the lines. Specifically, the line is produced by forming a metal layer and then by patterning the metal layer. To pattern the metal layer, a photoresist is deposited on the metal layer, and etching is further performed. In this process, the surface of the line is inevitably contaminated. Although the substrate is cleaned after the formation of the line, contamination may occasionally not be fully removed.
If an insulator layer is deposited on the line with the surface thereof contaminated, the insulator layer contains the contamination with no escape path left. When the line is now supplied with a voltage potential, migration tends to occur more easily between adjacent lines in the power supply voltage system than in other areas because the potential difference between the adjacent lines, namely, the magnitude of electric field is large there. When the line is contaminated, contamination is encapsulated by the insulator layer. The application of voltage fully establishes a condition under which migration easily occurs.
In accordance with the present invention, the insulator layer is formed clear of the area between the power source line and the ground line. In other words, no insulator layer is arranged between the power source line and the ground line. In this arrangement, contamination is not encapsulated by the insulator layer even if the lines in the supply voltage system are contaminated. Migration is thus prevented from being generated when a high-voltage is applied during driving.
Any of a variety of metals may be used for a metal forming the power source supply voltage system. The APC alloy is one of these metals. The APC may also be used for a material of a reflective layer. The reflective layer of the APC alloy provides a high reflectance in comparison with that of aluminum, while resulting in a low resistance wiring at the same time.
(2) A semiconductor chip mounting substrate of the present invention having a semiconductor chip mounted thereon, includes an output line to which an output signal is supplied from the semiconductor chip mounted on the semiconductor chip mounting substrate, a first region formed in a first side of the substrate, a second region formed in another side intersecting the first side of the substrate, a power source line, extending across the first region and the second region, for supplying a supply voltage potential to the semiconductor chip, a ground line, extending across the first region and the second region, for supplying a ground voltage potential to the semiconductor chip, an external circuit board connected, in the second region, to the ground line and the power source line, and an insulator layer for covering the output line, wherein the semiconductor chip is mounted in the first region, and the insulator layer is formed clear of (e.g., outside of) an area between the power source line and the ground line.
Since the power source line and the ground line extend across the first region and the second region in the semiconductor chip mounting substrate, the lines are lengthened. Migration occurs easily when the lines are lengthened, compared to when the length of the lines is short. If the present invention is implemented in the semiconductor chip mounting substrate having the above-referenced structure, the generation of migration is reliably controlled.
(3) The semiconductor chip mounting substrate of the present invention may further include a second semiconductor chip mounted in the second region, in addition to the first semiconductor chip mounted in the first region. With the number of semiconductor chips mounted on the substrate increasing, the possibility that lines having a large potential difference are adjacent to each other becomes high, and the generation of migration is more likely. If the present invention is implemented in that semiconductor chip mounting substrate, migration is reliably controlled.
(4) An electrooptical device of the present invention having an electrooptical layer, includes a substrate for supporting the electrooptical layer, an electrode for driving the electrooptical layer, a driving element mounted on the substrate, an output line, connected to the driving element, for supplying an output signal output from the driving element to the electrode, an insulator layer for covering the output line, a power source line, formed on the substrate, for supplying a supply voltage potential to the driving element, and a ground line, formed on the substrate, for supplying a ground voltage potential to the driving element, wherein the insulator layer is formed clear of an area between the power source line and the ground line.
The insulator layer is formed clear of the area between the power source line and the ground line in the electrooptical device. In this arrangement, contamination is not encapsulated by the insulator layer even if the lines in the supply voltage system are contaminated. Migration is thus prevented from being generated even when a high-voltage is applied during driving.
(5) In the electrooptical device of the present invention, the power source line may include a layer containing a metal as a major composition thereof. Since the electrical resistance of the line is set to be low, the electrical circuit is kept to a stabilized state, and the line may be extended even longer.
(6) In the electrooptical device of the present invention, the layer containing the metal as the major composition thereof may contain a metal selected from the group consisting of silver, palladium, and copper. An alloy containing all of silver, palladium, and copper is a so-called APC alloy. The APC alloy has an excellent light reflectance, and if the APC alloy is used for an reflective element in the electrooptical device, the display presents an image brighter than that presented by a device that employs Al (aluminum) for a light reflective element.
(7) In the electrooptical device of the present invention, at least one of the power source line and the ground line may include a laminate structure formed of a metal and a metal oxide. If the power source line and the ground line are fabricated of a metal alone, they are subject to corrosion and peeling. If the metal is covered with a metal oxide, corrosion and peeling are controlled. Further, if the power source line and the ground line are fabricated of a metal alone, an impurity dissolves from the metal, possibly contaminating the electrooptical material such as the liquid crystal or the electroluminescent material. With the metal covered with the metal oxide, however, such contamination is controlled.
(8) In the electrooptical device of the present invention, the electrooptical layer may be selected from an organic electroluminescent layer and a liquid-crystal layer. When the liquid-crystal layer is selected, the light transmitted through the liquid crystal is controlled by controlling the orientation of the liquid crystal, wherein polarized light transmitted through a polarizer and polarized light blocked by the polarizer are used to present a display. When the electroluminescent layer is selected, a display is presented by allowing organic electroluminescent elements to emit light on a per pixel basis.
(9) In the electrooptical device of the present invention, the electrooptical layer may be sandwiched between the electrode and a second electrode, and one of the electrode and the second electrode may be connected to a switching element. With this arrangement, a plurality of pixels forming the display area is turned on and off under the control of the switching element in the switching function thereof.
(10) In the electrooptical device of the present invention, the switching element may be selected from a thin-film transistor and a thin-film diode. The thin-film transistor is a three-terminal switching element. The thin-film diode is a two-terminal switching element.
(11) An electrooptical device of the present invention may further include a second electrode for driving the electrooptical layer. The electrooptical layer is sandwiched between the electrode and the second electrode, and includes a second driving element mounted on the substrate, an insulator layer for covering the output line, a second power source line, formed on the substrate, for supplying a supply voltage potential to the second driving element, and a second ground line, formed on the substrate, for supplying a ground voltage potential to the second driving element, and wherein the insulator layer is formed clear of an area between the second power source line and the second ground line.
The electrooptical device thus constructed includes two driving elements mounted on one substrate, and the insulator layer is formed clear of the area between the second power source line and the second ground line.
(12) An electrooptical device of the present invention having an electrooptical layer, includes a substrate for supporting the electrooptical layer, an electrode for driving the electrooptical layer, a driving element mounted on the substrate, an output line, connected to the driving element, for supplying an output signal output from the driving element to the electrode, an insulator layer for covering the output line, a power source line, formed on the substrate, for supplying a supply voltage potential to the driving element, a ground line, formed on the substrate, for supplying a ground voltage potential to the driving element, a control line, formed on the substrate, for supplying a control signal to control the driving element, and a data line, formed on the substrate, for supplying a data signal to the driving element. The insulator layer is formed clear of one of an area (1) between the power source line and the control line, an area (2) between the power source line and the data line, an area (3) between the ground line and the control line, and an area (4) between the ground line and the data line.
In the electrooptical device in this arrangement, the insulator layer is patterned in relation to the power source line and the ground line. Furthermore, the control line and the data line are also taken into consideration in the determination of the pattern of the insulator layer. With this arrangement, migration is controlled when a large potential difference takes place between a plurality of lines including the control line and the data line in the same way as when a large potential difference takes place between the power source line and the ground line.
(13) A liquid-crystal device of the present invention includes a first substrate having a first electrode, a second substrate having a second electrode and arranged to face the first substrate, a liquid-crystal layer interposed between the first electrode and the second electrode, a liquid-crystal driving IC mounted on a portion of the first substrate extending beyond the area thereof coextending with the second substrate, an output line, connected to the liquid-crystal driving IC, for supplying an output signal output from the liquid-crystal driving IC to one of the first electrode and the second electrode, an insulator layer for covering the output line, a power source line, formed on one of the first substrate and the second substrate, for supplying a supply voltage potential to the liquid-crystal driving IC, and a ground line, formed on one of the first substrate and the second substrate, for supplying a ground voltage potential to the liquid-crystal driving IC, wherein the insulator layer is formed clear of an area between the power source line and the ground line.
In the liquid-crystal device thus constructed, the insulator layer is formed clear of the area between the power source line and the ground line. In other words, no insulator layer is arranged between the power source line and the ground line. In this arrangement, contamination is not encapsulated by the insulator layer even if the lines in the supply voltage system are contaminated in the manufacturing process of the liquid-crystal device. Migration is thus prevented from being generated even when a high-voltage is applied during driving.
(14) In the liquid-crystal device of the present invention, the power source line may include a laminate structure containing a plurality of layers, and one of the first electrode and the second electrode, formed on the same substrate as that bearing the power source line, may also include a laminate structure of a plurality of layers. In other words, the electrode and the power source line formed on the same substrate are fabricated of the same layer structure. In this arrangement, the power source line and the electrode are concurrently fabricated in the same process. The manufacturing process is thus simplified.
(15) The liquid-crystal device of the present invention may further include a reflective layer, wherein the laminate structure contains a metal layer and a metal oxide layer formed on the metal layer, and wherein the metal layer is formed of the same layer as that forming the reflective layer. In this arrangement, the manufacturing process of the liquid-crystal device is simplified.
(16) A liquid-crystal device of the present invention includes a first substrate having a first electrode, a second substrate having a second electrode and arranged to face the first substrate, a liquid-crystal layer interposed between the first electrode and the second electrode, a first liquid-crystal driving IC mounted on a first side of the first substrate extending beyond the area thereof coextending with the second substrate, a second liquid-crystal driving IC mounted on an extending portion of a second side of the first substrate, intersecting the first side of the first substrate, a plurality of lines connected to one of the first liquid-crystal driving IC and the second liquid-crystal driving IC, and an insulator layer for covering several of the plurality of lines, wherein the plurality of lines includes a power source line for supplying a supply voltage potential to the first liquid-crystal driving IC and a ground line for supplying a ground voltage potential to the first liquid-crystal driving IC, and wherein the insulator layer is formed clear of an area between the power source line and the ground line.
The liquid-crystal device thus constructed includes two driving elements mounted on one substrate, and the insulator layer is formed clear of the area between the second power source line and the second ground line for the two liquid-crystal driving ICs.
(17) A liquid-crystal device includes a first substrate having a first electrode, a second substrate having a second electrode and arranged to face the first substrate, a liquid-crystal layer interposed between the first electrode and the second electrode, a liquid-crystal driving IC mounted on a portion of the first substrate extending beyond the area thereof coextending with the second substrate, an output line, connected to the liquid-crystal driving IC, for supplying an output signal output from the liquid-crystal driving IC to one of the first electrode and the second electrode, an insulator layer for covering the output line, a power source line, formed on one of the first substrate and the second substrate, for supplying a supply voltage potential to the liquid-crystal driving IC, a ground line, formed on one of the first substrate and the second substrate, for supplying a ground voltage potential to the liquid-crystal driving IC, a control line, formed on one of the first substrate and the second substrate, for supplying a control signal to control the liquid-crystal driving IC, and a data line, formed on one of the first substrate and the second substrate, for supplying a data signal to the liquid-crystal driving IC. The insulator layer is formed clear of one of an area (1) between the power source line and the control line, an area (2) between the power source line and the data line, an area (3) between the ground line and the control line, and an area (4) between the ground line and the data line.
In the liquid-crystal device in this arrangement, the insulator layer is patterned in relation to the power source line and the ground line. Furthermore, the control line and the data line are also taken into consideration in the determination of the pattern of the insulator layer. With this arrangement, migration is controlled when a large potential difference takes place between a plurality of lines including the control line and the data line in the same way as when a large potential difference takes place between the power source line and the ground line.
(18) An electroluminescent device of the present invention includes a base structure, a first electrode mounted on the base structure, an electroluminescent layer arranged on the first electrode, a second electrode arranged on the electroluminescent layer, a first driving IC mounted on a first side of the base structure, and connected to the first electrode, a second driving IC mounted on a second side of the base structure, intersecting the first side thereof, and connected to the second electrode, a power source line for supplying a supply voltage potential to one of the first driving IC and the second driving IC, a ground line for supplying a ground voltage potential to one of the first driving IC and the second driving IC, an output line to which an output signal output from one of the first driving IC and the second driving IC is supplied, and an insulator layer for covering the output line, wherein the insulator layer is formed clear of an area between the power source line and the ground line.
In the electroluminescent device thus constructed, the insulator layer is formed clear of the area between the power source line and the ground line. In other words, no insulator layer is arranged between the power source line and the ground line. In this arrangement, contamination is not encapsulated by the insulator layer even if the lines in the supply voltage system are contaminated in the manufacturing process of the electroluminescent device. Migration is thus prevented from being generated when a high-intensity electric field is applied during driving of the electroluminescent device.
(19) An electroluminescent device of the present invention includes a base structure, an anode electrode mounted on the base structure, an electroluminescent layer arranged on the anode electrode, a cathode electrode arranged on the electroluminescent layer, a first driving element connected to at least one of the anode electrode and the cathode electrode, a plurality of first input lines connected to the first driving element, and an insulator layer for covering several of the input lines, wherein the first input lines include a power source line for supplying a supply voltage potential to the first driving element and a ground line for supplying a ground voltage potential to the first driving element, and wherein the insulator layer is formed clear of an area between the power source line and the ground line.
In the electroluminescent device thus constructed, the insulator layer is formed clear of the area between the power source line and the ground line. In other words, no insulator layer is arranged between the power source line and the ground line. In this arrangement, contamination is not encapsulated by the insulator layer even if the lines in the supply voltage system are contaminated in the manufacturing process of the electroluminescent device. Migration is thus prevented from being generated even when a high-intensity electric field is applied during driving of the electroluminescent device.
(20) An electroluminescent device of the present invention includes a second driving element connected to the other of the anode electrode and the cathode electrode, an output line, connected to the second driving element, for supplying an output signal output from the second driving element to the other electrode, and a plurality of second input lines, formed on the base structure, for supplying an input signal to the second driving element, wherein the second input lines include a power source line for supplying a supply voltage potential to the second driving element and a ground line for supplying a ground voltage potential to the second driving element, and wherein the insulator layer is formed clear of an area between the power source line and the ground line.
In the electroluminescent device thus constructed, the insulator layer is formed clear of the area between the power source line and the ground line. In other words, no insulator layer is arranged between the power source line and the ground line. In this arrangement, contamination is not encapsulated by the insulator layer even if the lines in the supply voltage system are contaminated in the manufacturing process of the electroluminescent device. Migration is thus prevented from being generated even when a high-intensity electric field is applied during driving of the electroluminescent device.
(21) An electroluminescent device of the present invention includes a base structure, an anode electrode mounted on the base structure, an electroluminescent layer arranged on the anode electrode, a cathode electrode arranged on the electroluminescent layer, a driving element connected to at least one of the anode electrode and the cathode electrode, an output line, connected to the driving element, for supplying an output signal output from the driving element to one of the anode electrode and the cathode electrode, an insulator layer for covering the output line, a power source line, formed on the base structure, for supplying a supply voltage potential to the driving element, a ground line, formed on the base structure, for supplying a ground voltage potential to the driving element, a control line, formed on the base structure, for supplying a control signal to control the driving element, and a data line, formed on the base structure, for supplying a data signal to the driving element, wherein the insulator layer is formed clear of one of an area (1) between the power source line and the control line, an area (2) between the power source line and the data line, an area (3) between the ground line and the control line, and an area (4) between the ground line and the data line.
In the electroluminescent device in this arrangement, the insulator layer is patterned in relation to the power source line and the ground line. Furthermore, the control line and the data line are also taken into consideration in the determination of the pattern of the insulator layer. With this arrangement, migration is controlled when a large potential difference takes place between a plurality of lines including the control line and the data line in the same way as when a large potential difference takes place between the power source line and the ground line.
(22) Electronic equipment of the present invention includes as a display unit thereof an electrooptical device according to one of the above-referenced electrooptical devices. The electronic equipment, with the electrooptical device thereof free from migration during use, maintains the image quality thereof for a long period of time. The electronic equipment may be mobile equipment such as a mobile telephone or a mobile information terminal, or may be a video camera.